There is an atmosphere of crisis. In the darkness telephones can be heard ringing and anxious voices clamour for attention until one cooler, harder-edged voice takes charge, issuing orders, arranging press conferences, limiting damage.

Then the brand name - Aristotle - emerges on the blank television screen. Aristotle Publishing, one of a new breed of political hired guns in US politics, is currently running TV advertisements in Washington offering mastery of the world wide web to aspiring presidential candidates. According to its slogan, it provides "power tools" for politics.

The San Francisco-based firm of experts in cyber-campaigning claims to represent the politics of the future, in which candidates will be able to identify wavering voters or would-be recruits as they roam the internet, then bombard them with precision-tailored political advertising.

It is just one way in which the 2000 elections will mark a leap forward in the evolution of politics in the information age. In another telling development, Arizona Democrats will be allowed to cast their votes online in the party primary, in what is thought to be the first legally binding public election ever held on the internet. Most analysts expect the practice to spread.

There are about 30 significant companies now specialising in online politics, but Aristotle has emerged at the front of the pack, and is now running internet advertising campaigns for Republicans George W Bush and John McCain.

For Mr Bush, the party's frontrunner, Aristotle has developed an interactive banner advertisement, which appears across the top of hundreds of strategically chosen websites. Alongside a picture of a couple working on their tax returns, a message slides into place asking: "How much will the Bush tax cut save you? Find out right now in this banner... Click here now."

Clicking on the rectangle leads the would-be voter to a computerised form asking for information on earnings, marital status, number of children and so on. It instantly produces the savings the household would allegedly make by voting for the Texas governor.

The banner has so far appeared on 1,500 websites, including Yahoo, Excite and CNN.com.

Mr McCain has pursued a different strategy, using Aristotle banner advertisements to track down potential volunteers. His staff say that in a pilot campaign in Virginia, 192 people - about 2% of internet users to see his promotion - have so far clicked on the ads to find out more. And of those 192, about half volunteered to circulate campaign literature.

John Phillips, Aristotle's director, said: "This is the most interactive use of the internet for politics that we've seen to date, because it engages the voter. It's not like a one-way broadcast communication."

He argued that the ability to calculate exactly where and when to show the website ads made Aristotle's brand of political campaigning far more cost-effective. Referring to the New Hampshire primary, Mr Phillips said: "Your alternative, of buying television in the Boston market, means you're going to be hitting a lot of people who either don't care or can't vote. In this case, you're just targeting people who can vote for your candidate and you're able to do some pretty effective things."

But it is the cyber-campaign's capacity to seek out particular target groups that has aroused concerns about privacy and ethics. In choosing its targets, Aristotle uses information on Americans' viewing habits and personal lives which has been bought from other companies monitoring activity on the web. Each click on a website could potentially be turned into a piece of data in a political campaign.

Jay McAniff, an Aristotle spokesman, said the firm used only "permission-based marketing", based on information entered voluntarily by internet users. It does not use "cookies": internet programs which infiltrate computer systems and extract data about their users.

But Jacob Weisberg, a columnist writing in Slate online magazine, argued: "There's something Big Brother-ish about being bombarded with ads based on information you've given for another purpose.

"Imagine if your television was able to gather details about your viewing habits and your personal life and then transmit that data to companies that wanted to use it to sell you things. You might find it pretty creepy."